The present invention relates to a process monitoring device for sample processing apparatus and a control method of sample processing apparatus. In particular, the present invention relates to a process monitoring device for vacuum processing apparatus suitable for fine patterning of semiconductor devices and a control method of semiconductor device manufacturing apparatus utilizing the process monitoring device.
Year after year, critical dimensions of semiconductor devices are becoming finer and finer, and demands on dimension precision of patterning are becoming more and more strict. On the other hand, in a semiconductor manufacturing apparatus for patterning a semiconductor wafer physically or chemically by using heat and plasma, reaction products produced by a chemical reaction within the apparatus sticks to an internal wall of the apparatus and remains. Thus the reaction products often change the processing state of the wafer as processing goes on. Therefore, there is a problem that as the wafer processing is conducted on a large number of wafers the patterned shape of the semiconductor device gradually changes and the performance is degraded. In order to improve the situation, there are some countermeasures such as cleaning substances sticking to an internal wall of a chamber by using plasma and raising the temperature of the chamber wall to make substances hardly stick. In most cases, however, these countermeasures are not complete. Eventually, the patterned shape of the semiconductor devices gradually changes. Before the patterned shape changes so as to pose a problem, therefore, replacement or cleaning of parts of the manufacturing apparatus is conducted. Besides the deposited film, various variations of the apparatus state relate to variations of the wafer patterned shape. Therefore, there has been devised a contrivance such as detecting a change of the processing state within the semiconductor manufacturing apparatus, feeding back a result of detection to an input of a plasma processing apparatus, and keeping the processing state constant.
A method for monitoring such a variation of plasma processing is disclosed in, for example, JP-A-10-125660. In the disclosed example, there is shown a method of predicting the apparatus performance and diagnosing the plasma state by using model equations of relations between the plasma processing characteristic and electric signals of the apparatus. As its method, there is disclosed a method of deriving model equations representing relations between three electric signals and the plasma processing characteristic of the apparatus by using a multiple regression analysis. Another example is disclosed in JP-A-11-87323. In this disclosed example, there is shown a method of applying a typical detection system having a multiplicity of existing detectors attached thereto to a plasma processing apparatus and monitoring the apparatus state on the basis of the correlation signal of the detected signal. As a method for generating the correlation signal, model equations using ratios of six electric signals are disclosed. Another disclosure example is found in U.S. Pat. No. 5,658,423. In this disclosure example, there is shown a method of taking in light or a large number of a mass spectrometer, generating a correlation signal, and monitoring the apparatus state. As a method for generating this correlation signal, there is disclosed a method of using a principal component analysis.